The Duke and Duchess of Cambridge are racing each other on America's Cup yachts in Waitemata Harbour, their main public appearance in the biggest city.

Thousands of Aucklanders turned out to see Prince William and Catherine in their lunchtime public walk at the Viaduct Basin.

She is teamed with Team New Zealand skipper Dean Barker against Prince William and Team New Zealand manager Grant Dalton for the match race.

Prince William has the benefit of experience, having already sailed in one of the yachts in 2010.

He has been reported as saying his race against the Duchess to be "a bit of healthy competition" - although in the event it was one-sided with the Duchess winning both races. She patted her husband's shoulder and said "I'm sorry," but by all accounts did not look sorry to have punished her husband on the water.

The Duchess was on NZL41, the old Team New Zealand racer now used as a charter boat. The Duke was on to NZL68, once owned by a German syndicate that had planned to race in the 2003 America's Cup in Auckland.

The royal couple flew into Auckland for their relatively brief visit in an RNZAF Boeing 757 that landed Whenuapai Air Base where they were greeted by Auckland mayor Len Brown and about 100 family members of the base personnel.

Rain greeted the official party when it arrived for a drive around the Wynyard Quarter to the Team New Zealand base, where the Duke and Duchess were fitted out in yachting gear.

The rest of the day includes a Sealegs amphibian trip back to West Park Marina, Hobsonville, and then reboarding the 757 for the late afternoon flight returning the royal couple to Wellington.